The study compares the physiological and behavioural responses to diurnal heat of South African indigenous Windsnyer (WS) pigs and imported Large White (LW) pigs in the hot-wet season in South Africa. Rectal temperature, skin surface temperature, breathing rates and heart rate were each recorded three times per day every other day (0800 h, 1200 h, 1600 h) for a period of 105 days in 12 six-week old gilts of each breed. A completely randomised design was used. There were no differences (P > 0.05) in breathing rate and rectal temperature between the pig breeds. Skin surface temperatures and heart rate were higher (P < 0.05) for the LW pigs than WS pigs at all times of the day. Time of the day affected (P < 0.05) all physiological parameters which generally increased to a peak during mid-day before decreasing at 1600 h. The frequency and duration of wallowing, sprawling in slurry and lying in prostrate posture were higher in LW than WS pigs. Indigenous WS pigs had higher (P < 0.05) values for hair length, final hair density and fat thickness than the LW pigs. These findings suggest that WS pigs could be better at thermoregulation than LW pigs.